A conventional servovalve consists of a pilot stage controlling a mobile power distribution member of a power stage. The function of the power stage is to deliver a pressure or a flow rate proportional to an instruction sent to the pilot stage.
The pilot stage includes two hydraulic elements, namely a hydraulic sender (nozzle or ejector) and a hydraulic receiver (paddle, deflector or fixed receiver) modification of the relative position of which generates pressure differentials that are used for precise movement of a mobile power distribution member of the power stage of the servovalve. This mobile power distribution member slides in a cylindrical liner installed in the body of the servovalve. The position of the hydraulic sender or receiver is generally controlled by a torque motor that moves one of the hydraulic elements of the pilot stage relative to the other one. The movement of the mobile power distribution member in its liner then establishes communication between a set of drilled passages and openings the arrangement of which makes it possible to deliver a pressure or a flow rate proportional to the movement of said mobile power distribution member.
Ejector-type servovalves are well known for their high resistance to pollution of the fluid because of a greater distance between the fluid ejector and the deflector compared to the distance separating the nozzles and the paddle in a servovalve with nozzles and a paddle.
It is known to produce such ejector-type servovalves with a fluid ejector fastened to an element that can be twisted and that is built in at one or both of its two ends. Such servovalves require the use of powerful torque motors to apply a twisting torque to the element that can be twisted in order to move the fluid ejector. Such torque motors are heavy and consume a great deal of electrical energy.
Another known disadvantage of servovalves with a jet-type pilot stage is that it is necessary to route the fluid to the ejector over the power stage of the servovalve and its mobile power distribution member. This necessitates costly machining which, given the high pressures of the feed fluid, impose the provision of large additional thicknesses of material exclusively to accommodate the passage feeding fluid to the ejector. There is therefore a portion of the volume of the servovalve and therefore a portion of its weight dedicated to the provision of this passage.